The prevalence of breathing disorders during sleep, including snoring and sleep apnea, is relatively high. Such disorders are associated with significant morbidity.
The harsh and rough sound known as snoring is typically caused when a person breathes through his or her mouth during sleep in such a manner so as to cause the soft palate and/or uvula to vibrate, but may also occur when the person breathes through his or her nose. In addition to the irritating snoring sound which may cause potential marital stress, it has been suggested that mouth breathing is unhealthy. Indeed, it contributes to the development of gum diseases such as pyorrhoea and also to an unpleasant dry mouth syndrome.
Sleep apnea is a potentially lethal condition characterized by multiple mixed or obstructed apneas during sleep. Symptoms of sleep apnea include repetitive episodes of inordinately loud snoring and excessive daytime sleepiness.
The characteristic snoring pattern noted during sleep apnea is one in which inspiratory snores gradually increase when obstruction of the upper airway develops. A loud, choking inspiratory gasp then occurs as the respiratory efforts succeed in overcoming the occlusion.
The aroused individual subject to sleep apnea is usually aware of neither the breathing difficulty nor of the accompanying body movements that, at times, violently disturb his or her sleep. Typically, a diagnostic study is necessary for an adequate description of the problematic sleep breathing pattern.
Apneic episodes during sleep are typically defined as cessations of air flow at nose and mouth lasting 10 seconds or more. It can be readily documented by so-called poly-somnographic recordings.
There are varying degrees of apnea differentiated by the frequency of periodic breathing cessation episodes during sleep, and also the degree of hypoxia resulting from the related irregular breathing pattern.
When normal breathing is disrupted during sleep, an increased carbon dioxide level and a reduced oxygen level appear in the blood. The sleeping person is then suddenly aroused and gasps for air. This gasping for air is often accompanied by a loud snort.
An increased carbon dioxide level in the blood can cause adverse effects on the vital organs. The heart is usually caused to pump harder and at a higher rate in an effort to compensate for the lack of oxygen. Other organs, such as the kidneys and liver are suddenly confronted with increased blood flow and must adjust to cope with this change. This cycle may be repeated many times during a night's rest and often results in a general lack of proper rest and the restorative benefits thereof.
Some of the health related problems associated with sleep apnea include hypertension, stroke, irregular heartbeat, heart attack as well as the psychogenic conditions from the loss of restful sleep.
It is generally believed that the cause to this condition is a narrowing of the airways while sleeping. This is believed to be caused by a collapse of the tissue structures surrounding the airway. There seems, however, to be no consensus as to what tissue structures the condition should be-attributed to and as to why certain tissue structures close.
There are differing locations and patterns of pharyngeal collapse for each person. In addition to the physical findings and properties which characterize the pharynx in individuals with obstructive sleep apnea such as increased collapsibility, increase compliance, increased resistance and decreased cross-sectional area, the physical properties and spatial relationships of the pharyngeal airway, head and neck, as well as the neuromuscular integrity of the airway and a mechanism of breathing control must also be considered relevant in their contribution to the mechanism and precipitation of upper airway collapse.
In general, it may be considered that obstructive apnea occurs during sleep when the pharyngeal dilator muscle activity (genioglossus, the infrahyoid muscle and the palatal muscle group) that normally maintain airway potency during inspiration through dilation of the airways, is diminished. When the intraluminal negative pressure of the airway reaches a critical point, the combination of redundant tissues and the loss of pharyngeal muscle tonus cause airway collapse during inspiration. It should, however, be noted that obstruction has also been found to occur during expiration and inspiration.
The prior art is replete with various methods and devices that have been proposed in attempts to cure snoring and sleep apnea. Treatments available for sleep apnea vary from weight loss to surgical interventions to prosthetic devices. Although weight loss is the most desirable approach, few patients are able to comply with their diets and very few can afford to continue the exposure to the symptoms of sleep apnea for extended periods while losing sufficient weight to reduce or cure the disease.
Surgical approaches are only effective in about 50% of cases. They are also invasive, expensive and may produce undesirable side effects.
The most successful prosthetic device has been the nasal continuous positive airway ventilator or pressure known as “CPAP”. The advantages of the nasal CPAP system are that it produces immediate relief, is non-invasive and can be used while achieving weight loss, hence eliminating the need for surgery.
The CPAP technique, however, suffers from some important drawbacks. One of the primary drawbacks associated with nasal CPAP has been compliance. While nearly all patients are fitted with nasal CPAP as an initial treatment modality, many cease using the system after a few months. At least three primary factors have been identified as the cause for poor compliance amongst individuals using the CPAP system. One such factor is the lack of perfect fit and discomfort of wearing a nasal mask. The positive pressure of the ventilator flow is often mentioned as another factor. Some patients experience an uncomfortable and annoying sensation of forced air stream in their nose and mouth. Also, dry mouth and throat are often cited as the source of dissatisfaction with the sleep apnea ventilators known as CPAP.
Another type of devices used for treating sleep apnea is a valved nasal cannula insertable in the nostril of an intended user. Such cannulae typically include a body defining a passageway. A valve extends across the passageway and is configured to allow air to flow substantially unaffected into the nose of the intended user, but to restrict any outgoing flow of air so as to provide a backpressure, with the intention of keeping the airways open so as to reduce snoring.
Many such devices have a valve taking the form of a flexible leaflet extending across the passageway and attached to the body at the periphery thereof. This is the case, for example, of some of the nasal cannulae described in U.S. Pat. No. 6,626,179 issued Sep. 30, 2003 to Pedley, and of some of the cannula described in US Patent Application 2006/0150979 of Doshi et al. published Jul. 13, 2006. However, such leaflets may be influenced by gravity as the orientation of the leaflet relatively to its attachment point will influence its dynamic properties. Furthermore, these leaflets present a relatively large lever relatively to their attachment points and therefore have a relatively large response time when transitioning between their “free flowing” configurations to their “backpressure providing” configurations.
The above-referenced US Patent Application 2006/0150979 presents some valved nasal cannulae that alleviate at least in part these problems by having valves that are supported at the center thereof by a frame extending across the passageway. Also, some of the valves presented in this document are supported by the body of the cannula at two diametrically opposed location and fold in two to let air flow upon inspiration by the intended user. These two types of valves however may lead to the valve leaflet sticking to itself or to the relatively flat surfaces of the valve support, which again reduces response time and may even lead to valve malfunction.
Another problem of these valves resides in that if the valve becomes detached from the body of the cannula for any reason, the valve may be aspirated by the user of the valve and block the airways of this user.
Accordingly, there exists a need in the industry for an improved valved nasal cannula. An object of the present invention is therefore to provide an improved valved nasal cannula.